LOW-ALLOY STEEL FOR OIL WELL TUBE HAVING EXCELLENT SULFIDE STRESS CRACKING RESISTANCE

摘要

A low-alloy steel for use in an oil well tube having the following composition by mass: C: 0.20 to 0.35%; Si: 0.05 to 0.5%; Mn: 0.05 to 0.6%; P: 0.025% or less; S: 0.01% or less; Al: 0.005 to 0.100%; Mo: 0.8 to 3.0%; V: 0.05 to 0.25%; B: 0.0001 to 0.005%, N: 0.01% or less; O: 0.01% or less; and remainder: Fe and impurities, the composition satisfying the following requirement shown by the formula (1): 12V + 1 - Mo = 0 (1) wherein the symbol for each element represents the content of the element (% by mass). The low-alloy steel having this constitution shows an excellent SSC resistance.